Speedometer Cable, tranny end, 73 911

[moneymanager]

I've read several dozen threads on this subject; lots of people have had problems here. Some of the threads come close but none quite answers my question.
I've located the mechanical speedometer cable at the front of my 73 915 transmission. Various contributors talk of a hex shaped nut, or a knurled nut, securing the cable to the tranny. Mine is hex shape, just as in the PET diagrams, and huge...some say 24mm, some say 27mm. Mine also has two tiny tabs on its face, looking like they are there to help you with installation/removal as there is no wrench I know of which could remove this item, without pulling the front tranny support.
Can someone confirm that I want to turn the hex nut, and not something else?
Anyone know size?
Is there a wrench that fits in the available space somehow?
Can I support the tranny at the front and pull the mount to access the nut? I'm trying to disconnect this to pull the motor; should I lower the tranny a bit and pull it backward slightly to open up space to access this nut? This looks logical but

[moneymanager]

sorry. Forgot to finish sentence. Should read...This looks logical but potentially dangerous!
Thanks for any assistance. Jim

[moneymanager]

How often do people answer their own questions?
Yes, it is the hex nut that turns. If you are lucky, it will almost move with your fingers.
The wrench is a 27mm. The one that will reach this nut is open-end and bent about 30 degrees just above the head.
If you can't reach the hex nut with the wrench, support the tranny with a jack and loosen the two support bolts so that the tranny drops down just a bit. Careful, you don't want to let it come down very much, just enough to get your wrench into the tight space.